EUV lithography is anticipated to be the lithographic process of choice for producing future generations of semiconductor devices having linewidths on the order of 32 nm and smaller. The wavelength of the EUV radiation is nominally 13.5 nm, which calls for the use of specialized optics to collect and image the EUV radiation.
One type of EUV optical system used to collect the radiation from the light source is a grazing-incidence collector (GIC). A GIC typically comprises one or more concentrically arranged GIC shell mirrors (“GIC shells”). The GIC shells are configured to receive light from the EUV source at grazing incidence and reflect the light to form a focused illumination beam that first forms an intermediate focus and then creates an illumination region in the far field that is preferably uniform to within a specification set by the overall system optical design.
GICs typically require a “spider” that maintains the GIC shells in a secured position relative to one another. In some GICs, the GIC shells are secured to the spider using clips that engage the edge or outer surface of the shell and one of the spider spokes. To date, such clips have minimal or no adjustability, which makes optically aligning or adjusting the GIC shells problematic.